1. Field of the Invention
The present invention relates to a method of repairing shorts in an integrated circuit including a plurality of parallel-connected semiconductor elements such as vertical MOS transistors, vertical bi-polar transistors, etc., and more specifically to a method of lowering the incidence of defects in the assembly line production of the integrated circuit including a plurality of parallel-connected semiconductor elements.
2. Description of the Prior Art
Recently, various vertical semiconductor devices have been widely used in a number of industrial fields. This is because the vertical semiconductor devices are low in power supply voltage, high in input impedance but low in output impedance and high in switching speed, thus being well suitable for various switching circuits.
Typical examples of the above-mentioned vertical semiconductor devices include vertical MOS (Metal Oxide Semiconductor) transistors and vertical bi-polar transistors. In the case where the above-mentioned semiconductor devices are used for a power circuit in the form of an integrated circuit, the MOS transistors or the bi-polar transistors are usually connected in parallel with each other in order to increase the maximum current rated.
However, in the parallel-connected vertical semiconductor device as described above, in case any one of a plurality of semiconductor devices is determined to be defective due to, for instance, short-circuit or poor withstand voltage (poor breakdown voltage), in particular, between source and drain in a MOS transistor or between emitter and collector in a bi-polar transistor, or due to a pin hole formed in an insulating layer, the transistors cannot operate normally because they are connected in parallel with each other, resulting in the whole integrated circuit being discarded as a defective device. Further, in the assembly line production of such vertical semiconductor devices, it is necessary for inspectors to carefully check the short-circuit or poor withstand voltage between source and drain or between emitter and collector at all times and additionally to carefully handle the semiconductor devices.
In other words, in the assembly line production of parallel-connected vertical semiconductor devices, there exists a problem in that incidence of defects is high and therefore the manufacturing cost is also high.